The Helmholtz Association of German Research Centres is the largest scientific organisation in Germany. It is a union of 18 scientific-technical and biological-medical research centers. The official mission of the Association is "solving the grand challenges of science, society and industry". Scientists at Helmholtz therefore focus research on complex systems which affect human life and the environment. The namesake of the association is the German physiologist and physicist Hermann von Helmholtz.The annual budget of the Helmholtz Association amounts to more than 3.4 billion euros, of which about 70% is raised from public funds. The remaining 30% of the budget is acquired by the 18 individual Helmholtz Centres in the form of contract funding. The public funds are provided by the federal government and the rest by the States of Germany . Wikipedia.
Ahrens L.,Helmholtz Center Geesthacht
Journal of Environmental Monitoring | Year: 2011
The occurrence and fate of polyfluoroalkyl compounds (PFCs) in the aquatic environment has been recognized as one of the emerging issues in environmental chemistry. PFCs comprise a diverse group of chemicals that are widely used as processing additives during fluoropolymer production and as surfactants in consumer applications for over 50 years. PFCs are known to be persistent, bioaccumulative and have possible adverse effects on humans and wildlife. As a result, perfluorooctane sulfonate (PFOS) has been added to the persistent organic pollutants (POPs) list of the Stockholm Convention in May 2009. However, their homologues, neutral precursor compounds and new PFCs classes continue to be produced. In general, several PFCs from different classes have been detected ubiquitously in the aqueous environment while the concentrations usually range between pg and ng per litre for individual compounds. Sources of PFCs into the aqueous environment are both point sources (e.g., wastewater treatment plant effluents) and nonpoint sources (e.g., surface runoff). The detected congener composition in environmental samples depends on their physicochemical characteristics and may provide information to their sources and transport pathways. However, the dominant transport pathways of individual PFCs to remote regions have not been conclusively characterised to date. The objective of this article is to give an overview on existing knowledge of the occurrence, fate and processes of PFCs in the aquatic environment. Finally, this article identifies knowledge gaps, presents conclusions and recommendations for future work. © 2011 The Royal Society of Chemistry.
Mosler J.,Helmholtz Center Geesthacht
Computer Methods in Applied Mechanics and Engineering | Year: 2010
Variational constitutive updates provide a physically and mathematically sound framework for the numerical implementation of material models. In contrast to conventional schemes such as the return-mapping algorithm, they are directly and naturally based on the underlying variational principle. Hence, the resulting numerical scheme inherits all properties of that principle. In the present paper, focus is on a certain class of those variational methods which relies on energy minimization. Consequently, the algorithmic formulation is governed by energy minimization as well. Accordingly, standard optimization algorithms can be applied to solve the numerical problem. A further advantage compared to conventional approaches is the existence of a natural distance (semi metric) induced by the minimization principle. Such a distance is the foundation for error estimation and as a result, for adaptive finite elements methods. Though variational constitutive updates are relatively well developed for so-called standard dissipative solids, i.e., solids characterized by the normality rule, the more general case, i.e., generalized standard materials, is far from being understood. More precisely, (Int. J. Sol. Struct. 2009, 46:1676-1684) represents the first step towards this goal. In the present paper, a variational constitutive update suitable for a class of nonlinear kinematic hardening models at finite strains is presented. Two different prototypes of Armstrong-Frederick-type are re-formulated into the aforementioned variationally consistent framework. Numerical tests demonstrate the consistency of the resulting implementation. © 2010 Elsevier B.V.
Lilleodden E.,Helmholtz Center Geesthacht
Scripta Materialia | Year: 2010
The stress-strain response, slip mechanisms and size effect in Mg (0 0 0 1) single crystal was investigated by microcompression testing. It is found that plasticity occurs relatively homogeneously up to a critical stress, at which point a massive deformation occurs. While the yield stress increases with decreasing diameter, the qualitative behavior is independent of column size. Cross-sectional electron back-scattered diffraction measurements show that twinning is not the predominant deformation mechanism. © 2009 Acta Materialia Inc.
Lendlein A.,Helmholtz Center Geesthacht
Journal of Materials Chemistry | Year: 2010
Actively moving polymers that are stimuli-sensitive materials, which are able to shift their shape in response to suitable stimuli, have witnessed significant developments. The incorporation of magnetic nanoparticles into triple-shape polymer networks enables the non-contact activation of the triple-shape effect in an alternating magnetic field. The temperature dependence of water vapor permeability through a material related to the thermal transition of the switching domains has been used in textiles. Biomedical applications are an emerging application field for shape-memory polymers that has a significant role in minimally invasive surgery. The incorporation of inorganic nanoparticles or nano-fibers into shape-memory polymer matrices improves mechanical properties by reinforcement and retarding relaxation processes especially in thermoplastic polymers. The incorporation of nano-layered graphene in epoxy-based shape-memory polymers enhances scratching resistance and the thermal heating capability of the material.
Agency: Cordis | Branch: H2020 | Program: ERA-NET-Cofund | Phase: SC5-15-2015 | Award Amount: 50.73M | Year: 2016
In the last decade a significant number of projects and programmes in different domains of environmental monitoring and Earth observation have generated a substantial amount of data and knowledge on different aspects related to environmental quality and sustainability. Big data generated by in-situ or satellite platforms are being collected and archived with a plethora of systems and instruments making difficult the sharing of data and knowledge to stakeholders and policy makers for supporting key economic and societal sectors. The overarching goal of ERA-PLANET is to strengthen the European Research Area in the domain of Earth Observation in coherence with the European participation to Group on Earth Observation (GEO) and the Copernicus. The expected impact is to strengthen the European leadership within the forthcoming GEO 2015-2025 Work Plan. ERA-PLANET will reinforce the interface with user communities, whose needs the Global Earth Observation System of Systems (GEOSS) intends to address. It will provide more accurate, comprehensive and authoritative information to policy and decision-makers in key societal benefit areas, such as Smart cities and Resilient societies; Resource efficiency and Environmental management; Global changes and Environmental treaties; Polar areas and Natural resources. ERA-PLANET will provide advanced decision support tools and technologies aimed to better monitor our global environment and share the information and knowledge in different domain of Earth Observation.